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Side Effects of Anxiety Medications in Dogs

Dogs experiencing compulsive behaviors, separation anxiety, chronic pain, and other conditions may find relief from medications that influence serotonin levels in the body. Serotonin, a neurotransmitter, operates in the brain and nervous system, regulating various functions such as behavior, pain perception, appetite, movement, body temperature, as well as the heart and lung functions.

When a dog is prescribed multiple medications that raise serotonin levels simultaneously, it can lead to a condition known as serotonin syndrome (SS). If left untreated, SS can potentially be fatal.

Symptoms and Types

Just like in humans, serotonin syndrome in dogs can exhibit the following symptoms:

  • Changes in mental state (confusion, depression, or hyperactivity)
  • Difficulty with walking
  • Tremors and seizures
  • Vomiting
  • Diarrhea
  • Fast breathing (tachypnea)
  • Elevated heart rate (tachycardia)
  • Increased body temperature (hyperthermia)


The increased use of antidepressant drugs prescribed for humans is becoming more common in veterinary medicine. These medications modify serotonin levels in the body, thereby affecting mood and behaviors. Some frequently used antidepressants for dogs include buspirone, fluoxetine, and clomipramine.

Serotonin syndrome can occur under the following circumstances:

  • Excessive administration of antidepressants for dogs
  • Ingestion of other drugs that impact serotonin levels (such as amphetamines, chlorpheniramine, fentanyl, lithium, LSD)
  • Dogs with a heightened sensitivity to serotonin-altering substances
  • Consumption of certain foods alongside medications (e.g., cheese, anything containing L-tryptophan)

Signs of serotonin syndrome typically manifest quickly in dogs, appearing anywhere from 10 minutes to four hours after ingestion.


Your veterinarian will perform blood tests to assess the possibility of infection in your dog and to identify any ingested substances. Neurological assessments, including reflex and coordination measurements, will also be conducted to pinpoint affected areas of the nervous system, such as the brain or spinal cord. There isn’t a specific test available to definitively diagnose serotonin syndrome. Instead, the diagnosis relies on the history of drug ingestion and the observed symptoms in your dog.


The treatment for serotonin syndrome in dogs focuses on stabilizing and sedating the dog. If detected early (within 30 minutes), substances like activated charcoal may be administered orally to reduce the absorption of the drug into the dog’s system. If the dog is stable and the condition is caught early enough while the drug is still in the stomach, inducing vomiting or performing stomach pumping may help eliminate the drug from the body.

Symptoms of serotonin syndrome typically subside over a 24-hour period. During this time, close monitoring of the dog is essential. Medications may be administered to counteract the excess serotonin and alleviate severe seizures. Any medications that elevate serotonin levels in the dog are discontinued, and supportive care such as intravenous fluids is provided. With prompt treatment, the likelihood of death from this condition is reduced.

Living and Management

When administering medications known to influence serotonin levels in the body to animals, caution must be exercised. Avoid giving these medications in combination with foods containing L-tryptophan, such as dairy products, turkey, red meats, bananas, and peanut butter.


To prevent adverse reactions, avoid administering medications that elevate serotonin levels to animals already prescribed antidepressants. Your veterinarian should have full knowledge of all medications administered to your dog and should carefully select drug combinations.

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